The women-only chain was No. 2 on the list in 2004 and 2005, No. 3 in 2006 and No. 15 in 2007. Then Curves began a downward spiral, falling to No. 185 in 2008 and all the way to No. 381 last year.

This year, Curves is nowhere to be seen on the Franchise 500 list. Curves Founder and CEO Gary Heavin says the company simply could not sustain its growth rate in the United States after reaching 10,000 locations over a decade's time.

“We've reached our potential in the U.S. market and are currently experiencing excellent growth in nearly 80 countries,” Heavin says. “We are about seven times bigger than the next largest fitness club company, which means that we are helping more women — millions worldwide — move away from illness and chronic disease. And that's what really matters.”